Anatotitan

Anatotitan was an herbivore, a plant eater. It probably ate conifer needles, twigs, seeds, and other plant material with its tough beak. It had no teeth in its beak, but had hundreds of cheek teeth used for grinding up the tough plant material that it ate. Anatotitan had three rows of replacable teeth for a total of 720 teeth - it a tooth broke off, another replaced it.Anatotitan could run on two legs or walk on four. It may have gone on all four legs to graze low-lying plants. It was not a very speedy dinosaur.
Anatotitan fossils have been found in Montana and South Dakota, USA. It was named by Ralph Chapman and Michael K. Brett-Surman in 1990. Anatotitan was originally called Anatosaurus (Lull & Wright, 1942). Anatotitan was a late Ornithischian dinosaur, the order of bird-hipped, herbivorous dinosaurs. It was a member of the suborder Ornithopoda, and the family of duck-billed, herding herbivores, the hadrosaurs. Other hadrosaurs include Maiasaura, Lambeosaurus, Parasaurolophus, Corythosaurus, and Saurolophus.

Anatotitan was a large, duck-billed dinosaur about 33 feet (10 m) long and 8 feet (2.5 m) tall at the hips; it weighed roughly 5 tons (7300 kg) - about as big as a bus. It was very similar to Edmontosaurus, but it was more lightly built and had longer legs. Anatotitan had short arms, a long, pointy tail, three hoofed toes, mitten-like hands, a flat, sloping head with a wide, toothless beak, cheek pouches, and hundreds of closely-packed cheek teeth (for grinding plant material).
Anatotitan was a biped (it walked on two legs) but it could also walk on four legs, perhaps to graze low-lying plants. Anatotitan was probably a relatively slow-moving dinosaur with few defenses, but may have had keen senses (eyesight, hearing, and smell) to help it avoid predators. Anatotitan lived in the late Cretaceous period, about 70-65 million years ago, toward the end of the Mesozoic Era. It went extinct during the huge K-T mass extinction. T. rex and Dromaeosaurus were among its contemporaries, and they may have preyed upon Anatotitan. Anatotitan was an ornithopod, whose intelligence (as measured by its relative brain to body weight, or EQ) was midway among the dinosaurs.